JP2005317727A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck having multiple projections at an absorption face, including the dielectric substance, electrode and base substance for which the time taken for object desorption becomes longer than the desorption time in vaccum, when a evacuation process for treating the object to be absorbed is finished and the ambience of the electrostatic zipper returns to atmospheric pressure or a low-vaccum state, even if the projection height is small. <P>SOLUTION: This electrostatic chuck has a dielectric substance, electrode and base substance and has a number of projections 6 on the absorption face of the dielectric substance, and at least one groove 9 at the bottom of the absorption face that reaches the outer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electrostatic chuck used in semiconductor and liquid crystal fields such as a semiconductor device manufacturing apparatus and a liquid crystal device manufacturing apparatus.

  When manufacturing semiconductor devices and liquid crystal devices, electrostatic chucks capable of surface adsorption from the conventional mechanical clamp method are being studied to hold silicon wafers, glass substrates and the like, particularly in a vacuum atmosphere.

As the structure of the electrostatic chuck, for example, as described in Patent Document 1, a structure in which a plastic dielectric material is bonded on an insulator layer in which an electrode is embedded is known.
In addition, as described in Patent Documents 2, 3, and 4, there is known one in which an electrode is provided between two insulating ceramic plates.
Further, as described in Patent Document 5, an electrode in which an electrode on an insulating ceramic plate is coated with an insulating ceramic by a thermal spraying method is known.

JP-A-53-77489 (page 1-3, FIG. 1) JP-A-63-95644 (page 3-4, FIG. 1) JP-A-4-206545 (page 1-5, FIGS. 1 and 2) Japanese Patent Laid-Open No. 5-36819 (page 1-5, FIG. 1) JP 59-152636 A (page 1-4, FIG. 3)

  An electrostatic chuck is generally composed of a dielectric, an electrode, and a substrate. Electrostatic chucks such as Coulomb force, Johnson labeling force, and gradient force generated when a potential difference is applied between the electrode and an object to be adsorbed. The object to be adsorbed is held and fixed by the adsorption force.

In addition, in order to avoid pinching of minute foreign substances called particles and adhesion to the object to be attracted, protrusion processing may be performed on the attracting surface of the electrostatic chuck to reduce the contact area with the object to be attracted.

However, since the adsorption force decreases when the projection height dimension is increased, Patent Document 6 describes a technique for reducing the projection height dimension to several tens of microns or less.
Japanese Patent Publication No. 7-55423 (2nd page)

  Then, when the present inventors further investigated about the technique shown above, it turned out that the problem shown below arises. That is, when the vacuum process for processing the object to be adsorbed in vacuum is completed and the periphery of the electrostatic chuck is returned to the atmospheric pressure or the low vacuum state, the object to be adsorbed is brought into contact with the electrostatic chuck attracting surface if the height of the protrusion is small. It takes time until the pressure in the gap between the object to be adsorbed and the adsorption surface increases, and the desorption time until the object to be desorbed becomes longer than the desorption time in vacuum. For this reason, it is necessary to add a complicated mechanism to the apparatus, such as desorbing an adsorbed substance in a vacuum after the vacuum process and returning it to an atmospheric pressure or low vacuum state.

  In order to solve the above problem, the present invention has completed the vacuum process of processing the object to be adsorbed in vacuum even if the height of the protrusion is small, and returned the surroundings of the electrostatic chuck to atmospheric pressure or low vacuum. The desorption time until the object to be adsorbed can be desorbed does not become longer than the desorption time in vacuum. An electrostatic chuck is provided.

  The present invention provides an electrostatic chuck including a dielectric, an electrode, and a substrate, wherein the dielectric attracting surface has a plurality of protrusions, and one or more grooves reaching the outer periphery are formed on the bottom surface below the attracting surface. It relates to an electrostatic chuck.

  The electrostatic chuck according to the present invention has a small protrusion height dimension, and when the periphery of the electrostatic chuck is returned to the atmospheric pressure or low vacuum state after the vacuum process for processing the object to be attracted in vacuum is completed, The desorption time until the adsorbate can be desorbed can be prevented from becoming longer than the desorption time in vacuum, which is extremely suitable industrially.

As the dielectric material used in the electrostatic chuck of the present invention, ceramic materials such as Al ₂ O ₃ , Si ₃ N ₄ , AlN, SiC, and BaTiO ₃ are generally used, but they form protrusions and grooves. If possible, an epoxy resin, a polyimide resin, or the like can also be used.

  In addition, when the dielectric is a ceramic material, the electrode formed on the dielectric is formed, for example, by baking a paste made of glass with Ag-Pd, W, Ag, Au, or the like, or by firing simultaneously with the ceramic. Can do. On the other hand, when using resin etc. for a dielectric material, it can form by sticking metal plates, such as Al and Cu, and foil.

  In the present invention, it is preferable that the electrode for generating the electrostatic attraction force does not protrude from the side surface of the electrostatic chuck. As long as it does not protrude from the side surface of the electrostatic chuck, the dielectric, the base and the electrode can be integrated, or the dielectric on which the electrode for generating the electrostatic adsorption force is formed can be attached to another base. I do not care.

Usually, the plurality of protrusions are formed on almost the entire surface of the suction surface, but it is preferable to reduce the contact area for the purpose of avoiding the above-described foreign object pinching and adhesion. The groove reaching the outer periphery formed on the bottom surface below the adsorption surface may be formed in a part of the bottom surface, and the entire bottom surface may be a groove without any particular limitation. If the number of grooves is one, the effect of the present invention can be exhibited, but a plurality of grooves is more preferable. As for the depth of the groove, the effect of the present invention is exhibited as long as the groove can be formed on the bottom surface below the suction surface. However, the depth is preferable, and the dimension is more preferably larger than the height of the protrusion.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view of the vicinity of a suction surface of an electrostatic chuck having a plurality of protrusions on the suction surface according to an embodiment of the present invention and having 10 grooves reaching the outer periphery on the bottom surface below the suction surface; 2 is a plan view thereof, FIG. 3 is an enlarged cross-sectional view of the vicinity of the suction surface of the electrostatic chuck having only a plurality of protrusions on the suction surface of the comparative example (conventional), FIG. 4 is a plan view thereof, and FIG. FIG. 2 is a schematic diagram showing a cross section of an electric chuck and a circuit when adsorbing and desorbing an object to be adsorbed, where 1 is a dielectric, 2 is an object to be adsorbed, 3 is an electrode, 4 is a base, 5 is a switch, and 6 is a protrusion. , 7 is a bottom surface below the suction surface, 8 is a gap space, 9 is a groove reaching the outer periphery, and 10 is an electrostatic chuck.

  First, problems of the prior art will be described with reference to FIGS. When an electrostatic chuck is installed in a vacuum and a thin flat object to be adsorbed 2 such as a silicon wafer is adsorbed, a gap space 8 surrounded by the bottom surface 7 below the adsorbing surface, the object to be adsorbed 2 and the protrusion 6 is provided. Is in a vacuum state equivalent to that around the electrostatic chuck. When the periphery of the electrostatic chuck is returned to the atmospheric pressure or low vacuum state after the vacuum process is completed, if the height of the protrusion is small, it becomes difficult for the gas around the electrostatic chuck to flow into the gap space 8, and the gap space 8 is static. The pressure is lower than that around the electric chuck. Due to the pressure difference, the force to be pressed against the electrostatic chuck acts on the object to be attracted 2. Further, the adsorbed object 2 is deformed in the direction in which the volume of the gap space 8 decreases due to the pressing force, and the gas around the electrostatic chuck is more difficult to flow into the gap space 8. Therefore, the desorption time until the object to be adsorbed can be desorbed is longer than the desorption time in vacuum.

Therefore, when the electrostatic chuck according to the embodiment of the present invention shown in FIG. 1 and FIG. 2 is used, when the periphery of the electrostatic chuck is returned to the atmospheric pressure or low vacuum state after the completion of the vacuum process, the bottom surface below the adsorption surface. The gas around the electrostatic chuck flows through the groove 9 reaching the outer periphery formed in 7 and the bottom surface 7 below the adsorption surface quickly becomes the same pressure as the periphery of the electrostatic chuck. Therefore, like the electrostatic chuck of the comparative example (conventional) shown in FIGS. 3 and 4 having only a plurality of protrusions on the attracting surface, the force to be pressed against the electrostatic chuck 2 acts on the attracted object 2. The desorption time until the adsorbed object 2 can be desorbed does not become longer than the desorption time in vacuum.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Example 1
As shown in FIGS. 1 and 2, SiC (trade name: Hexalloy, manufactured by Hitachi Chemical Co., Ltd.) having a volume resistivity of 1 × 10 ⁹ Ωm, a diameter of 200 mm, and a thickness of 2 mm is used as the dielectric 1. Got ready.
Next, a quick-drying conductive paste (trade name: Sylbest, manufactured by Tokoku Chemical Laboratory Co., Ltd.) having a diameter of 198 mm and concentric with the dielectric 1 is applied to one surface of the dielectric 1 (the surface opposite to the adsorption surface). Then, it was naturally dried to form an electrode 3 having a thickness of 10 μm.

Thereafter, Al ₂ O ₃ (Hitachi Chemical Industry Co., Ltd.) having a volume resistivity of 1 × 10 ¹³ Ωm as the substrate 4 and the same dimensions as the dielectric 1 on the surface of the dielectric 1 on which the electrode 3 is formed, and having a hole in the center. Substrate 4 made by Co., Ltd. and trade name Halox) was attached with an insulating adhesive. A voltage is supplied to the electrode 3 through the hole in the center.

  Next, after flattening the suction surface and the surface opposite to the suction surface, as shown in FIG. 1, a protrusion having a of 4 mm, b of 1 mm and c (height) of 10 μm (dimension 1 mm) (× 1 mm × 10 μm) 6 was formed on the entire surface. Further, as shown in FIG. 2, d is 200 μm and e is 1 mm in size, and as shown in FIG. Ten electrostatic chucks were formed.

Comparative Example 1
As shown in FIGS. 3 and 4, an electrostatic chuck was obtained through the same material as in Example 1 and the same process as in Example 1 except that no groove was formed in the bottom surface 7 below the attracting surface.

  Next, the following comparative tests were performed using the electrostatic chuck obtained in Example 1 and the electrostatic chuck obtained in Comparative Example 1. In the comparative test, a silicon wafer having a diameter of 100 mm was used as an object to be adsorbed. In the test, a silicon wafer was placed on the suction surface of the electrostatic chuck in a vacuum container, and a voltage was applied to the electrode 3 by the circuit shown in FIG. Thereafter, when the inside of the container is kept in a vacuum after performing the desorption operation for switching the switch 5, and after 10 seconds after the desorption operation, dry air is introduced into the container so that the pressure inside the container becomes atmospheric pressure. When the inside was kept at atmospheric pressure, the operation of peeling the silicon wafer from the electrostatic chuck was performed to determine whether or not detachment was possible. The results are shown in Table 1.

  When the inside of the container was kept in a vacuum state even after the detachment operation, the silicon wafer was peeled off from the electrostatic chuck and detached in 10 seconds after the detachment operation in both Example 1 and Comparative Example 1. When the internal pressure of the container was changed to atmospheric pressure after the detachment operation, the silicon wafer was peeled off from the electrostatic chuck in 10 seconds after the detachment operation in Example 1, whereas it was detached in Comparative Example 1. It took 100 seconds after the desorption operation until the film could be peeled off and desorbed. In Comparative Example 1, when the elapsed time after the detachment operation was 50 seconds or less, the silicon wafer was damaged when the silicon wafer was peeled off from the electrostatic chuck.

  From the above results, the electrostatic chuck according to the embodiment of the present invention is detached when the object is adsorbed in vacuum and then returned to the atmospheric pressure or low vacuum state around the electrostatic chuck. The desorption time until it becomes possible does not become longer than the desorption time in vacuum. On the other hand, the electrostatic chuck of the comparative example (conventional) is capable of detaching the object to be adsorbed when the object is adsorbed in a vacuum and then returned to the atmospheric pressure or low vacuum state around the electrostatic chuck. It is clear that the desorption time until becomes longer than the desorption time in vacuum.

  The effect of the present invention was confirmed by a monopolar electrostatic chuck that gives a potential difference between the electrode and the object to be adsorbed, but a bipolar type that adsorbs the object to be adsorbed by giving a potential difference between a plurality of electrodes. The same effect can be obtained with this electrostatic chuck.

It is a cross-sectional enlarged view of the vicinity of the suction surface of the electrostatic chuck having a plurality of protrusions on the suction surface according to the embodiment of the present invention and having 10 grooves reaching the outer periphery on the bottom surface below the suction surface. It is a top view of FIG. It is a cross-sectional enlarged view of the vicinity of the suction surface of an electrostatic chuck having only a plurality of protrusions on the suction surface of a comparative example (conventional). FIG. 4 is a plan view of FIG. 3. It is the schematic which shows the circuit when adsorbing | sucking and desorb | sucking the to-be-adsorbed object and the cross section of an electrostatic chuck.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric 2 Adsorbed object 3 Electrode 4 Base | substrate 5 Switch 6 Protrusion 7 Bottom face under adsorption surface 8 Gap space 9 Groove reaching the outer periphery 10 Electrostatic chuck

Claims (1)

In an electrostatic chuck including a dielectric, an electrode, and a substrate, an electrostatic chuck having a plurality of protrusions on the suction surface of the dielectric and one or more grooves reaching the outer periphery on the bottom surface below the suction surface. Chuck.

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